498 



ADVENTURES IX RADIOISOTOPE RESEARCH 



ing way. The number of phosphate ions penetrating into the corpuscles 

 is proportional to the number of phosphate ions present in the plasma. 

 If no excess phosphate is added to the plasma for each phosphate ion 

 penetrating into the corpuscles a phosphate ion will move from the cor- 

 puscles into the plasma, since otherwise a constant decrease in the phos- 

 phate concentration of the plasma would take place. That an incessant 

 interchange of phosphate between plasma and corpuscles takes place can 

 be shown by adding labelled phosphate of negligible weight to the 

 plasma. As long as the^^P concentration of the corpuscle inorganic P is 

 lower than the ^^P concentration of the plasma inorganic P — what is 

 always the case, except for experiments of long duration — a ^^P atom 

 penetrating from the plasma into the corpuscles will be replaced by a 

 ^iP atom moving in the opposite direction and, correspondingly, an 

 accumulation of ^^F will take place in the corpuscles. If, by replacing 

 a portion of the plasma chloride by phosphate, the phosphate concentra- 

 tion is raised to twice its original value, during the same time twice as 

 many P atoms will penetrate from this plasma into the corpuscles than 

 from the normal plasma. The radio-phosphate ions moving from the 

 plasma into the corpuscles will now be replaced partly by stable phos- 

 phate and partly by chloride or other anions present in the corpuscles. 

 Since the stable phosphate obviously behaves in the same way as the 

 radiophosphatc, the phosphate ions penetrating into the corpuscles will 

 be replaced by phosphate, chloride or other anions previously located 

 in the corpuscles. The amount of phosphorus replaced in the plasma 

 by chloride (other anions) originally present in the corpuscles can be 

 determined by measuring the decrease in the P content of the plasma, 

 the amount of plasma P replaced by corpuscle P, however, by deter- 

 mining the percentage of ^^P which is to be found in the corpuscles. 

 If we find, for example, by radioactive measurement that 20 per cent 

 of the ^^P and by chemical determination that 10 per cent of the ^^P 

 left the plasma after raising the plasma phosphate concentration by 

 adding some excess phosphate and ^^P, we can conclude that half of the 



Table .5. — Distribution of ^^p between Plasma and Corpuscles 

 OF the Rabbit in Experiments in vitro at 37° 



a) 

 b) 



70 

 70 



90 

 90 



32p of negligible weight 



32p -j- 8 fold increase of plasma phos- 

 phate 



i 32p of negligible weight 



32p -|- 7 fold increase of plasma plios- 

 phate 



19.7 



21.4 

 32.0 



32.1 



